Magnetfluide als Dichtmaterial in Drehdurchführungen sorgen für höchste Reinheit im Vakuum

Rotary feedthroughs are used whereever rotary motions have to be transmitted into a vacuum chamber. These rotary feedthroughs have to constructed with a sealing technique which hermetically isolates the vacuum side from the ambient space in order to avoid any contamination inside the vacuum chamber. Magnetic fluids as the sealing technology is the adequate solution. We describe the principle of Magnetic Fluids and several applications of Magnetic Fluids used as the sealing technology in rotary feedthroughs.     

Ventilwerkstoffe für Verbrennungsmotoren

Valve Materials for Combustion Engines An overview is being given on production numbers, requirements and properties of valve materials. Their development from the beginning till today's state of the art is reviewed with a focus on Chromium-Manganese-Nitrogen-alloys. Valve materials are grouped by the criteria of density – heavy, lightweight – and alloying elements. The multiple stresses of the material in the valve are being met with a few standardised grades and specific ways of manufacture. The path of the material from bar stock to the finished valve is being followed. Engine development in the past decades increased the load on the valves which could be met by continuously developing their structural strength. Also the strength of all valve materials could be raised to nominal strength above 1100 Mpa by applying specific methods. Higher strength at the surface is being effectuated by work hardening effects. The technology to increase reliability of hollow valves and new aspects of valve seat facing including residual stress is explicitly discussed. General aspects of alloy utilisation is followed by a discussion of lightweight valve materials as Titanium alloys, intermetallic Titaniumaluminide alloys and ceramic materials, spec. Silicon Nitride, which all have a potential as forthcoming valve materials capable of reducing fuel consumption of the engines.     

Membrantechnologien für Vakuumpumpen

Diaphragm Technologies for Vacuum Pumps Diaphragm vacuum pumps are used in chemistry and as roughing pumps for high vacuum systems. Both planar diaphragms and moulded (also as »structured«) diaphragms are common. Long term tests confirmed that after some hundred hours of operation the ultimate vacuum of pumps with moulded diaphragms deteriorates due to fatigue and abrasion of the elastomer. In addition the pumping speed curve of moulded diaphragms is unfavourable for practical applications. Planar diaphragm pumps show a superior pumping speed curve and — depending on manufacturing quality — a stable performance over the whole lifetime in excess of 10,000 hours.     

Anstrengungshypothese für Metallklebverbindungen

Macroscopic Failure Criterion for Metal-to-Metal Bonds In order to judge the load limit of metal-to-metal bonds, one needs, on one hand, characteristic values of strength which can obtained by experimentation with a defined state of stress, and on the other hand, failure criteria which determine stressability caused by any multidimensional state of stress in comparison to the strength characteristics obtained. Starting from the theory of the plastic potential for polymers, a failure criterion is formulated for metal-to-metal bonds. It is assumed that the adhesive-bonded joint is an homogeneous isotropic body. The evalution of some of the experimental results given in the literature on the subject show that the failure criterion for quasistatic loaded metal-to-metal bonds can be applied.     

Erosionsschutzschichten für Flugtriebwerke

Erosion Resistant Coatings for Aircraft Engines Under certain operation conditions, increased amounts of sand particles may be injected into the air inlet duct of jet engines. Because of the high air speed and the high velocity of the compressor blades, an intense material removal from the airfoils by erosion can occur, resulting in a significant deterioration of their functionality. By protecting the airfoils with a special protective coating, a considerable extension of the service life can be achieved.     

Werkstoffkennwerte für die Lebensdauerberechnung von Strukturen aus Stahlfeinblechen für den Automobilbau

Materials Data for Fatigue Life Calculation of Steel Sheet Structures for Automotive Engineering Within a joint project of the steel and automotive industry 17 steel sheet materials for automotive engineering in various delivery and forming conditions at temperatures of –40 °C, 22 °C and 100 °C were investigated. In the course of 37 test series strain controlled fatigue curves to crack initiation and stress‐strain‐curves under monotonic and cyclic loading were determined. All experimental data, hysteresis loops and determined cyclic properties are available in a database. A correlation between the mechanical properties from tensile tests and the properties from strain controlled cyclic experiments seems to be possible.